Polycarbosilanes are useful as photoreactive materials, such as photoresists, and as raw materials of silicon carbide-series ceramics. To produce polycarbosilanes, the following methods are known:
1) a method in which polysilanes are subjected to a thermal transformation reaction; PA0 2) a method in which dihalosilanes, dihalopolysilanes, or their equivalents (e.g., bifunctional silicon compounds, such as dialkoxysilanes, bis(dialkylamino)silanes, and dialkylthiosilanes) are subjected to a polycondensation reaction with organic dianions, such as di-Grignard reagents or dilithio organic compounds; PA0 3) a method in which bis(chlorosilyl) organic compounds or their equivalents (e.g., compounds having two functional silyl groups in a molecule, such as bis(bromosilyl) organic compounds) are subjected to a polycondensation reaction by the Wurtz reaction; and PA0 4) a method in which dihydrosilanes, or dihydropolysilanes, and dienes are subjected to hydrosilylation polymerization. PA0 (1) a method for producing polycarbosilanes, comprising polymerizing silane of the formula SiH.sub.4 with dienes in the presence of a rare earth metal complex; PA0 (2) the method for producing polycarbosilanes as stated in the above (1), wherein the dienes are .alpha.,.omega.-alkadienes; PA0 (3) the method for producing polycarbosilanes as stated in the above (1) or (2), wherein the rare earth metal complex is an organic neodymium complex; and PA0 (4) the method for producing polycarbosilanes as stated in the above (3), wherein the organic neodymium complex is Cp*.sub.2 NdCH(SiMe.sub.3).sub.2, wherein Cp* represents a pentamethylcyclopentadienyl group, and Me represents a methyl group.
However, these methods have the following respective problems. That is, with respect to the method 1), because of the high temperature pyrolysis necessary to the transformation reaction, the structure of the product is irregular and it is difficult to control the reaction to obtain polycarbosilanes having the intended structure. With respect to the methods 2) and 3), the reaction uses halosilanes, which are sensitive to moisture and corrosive, and in addition, compounds that ignite spontaneously in air and sensitive to moisture, such as alkali metals, organic alkali metal compounds, and Grignard reagents, are treated. Therefore, the reaction is dangerous. The high reactivity of the reactants causes a limitation of these methods to the synthesis of compounds having sensitive functional groups. With respect to the method 4), which uses hydrosilylation polymerization, in comparison with the reactions of 1) to 3), desired polycarbosilanes can be easily designed and synthesized and the reaction conditions are mild. However, in the case of hydrosilylation reaction using silane of the molecular formula SiH4, since it is considered that the transition metal complex catalyst used in the reaction is deactivated conspicuously (M. Itoh, K. Iwata, R. Takeuchi, and M. Kobayashi, J. Organomet. Chem., 420, C5 (1991)), it has not been attempted to carry out hydrosilylation polymerization using silane (SiH.sub.4).